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Signed-off-by: Daniel Vetter Cc: Thomas Zimmermann Cc: Sumit Semwal Cc: "Christian König" Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org --- drivers/dma-buf/dma-buf.c | 20 ++++++++++++++------ include/linux/dma-buf.h | 25 +++++++++---------------- 2 files changed, 23 insertions(+), 22 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index e63684d4cd90..a12fdffa130f 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -1001,15 +1001,15 @@ EXPORT_SYMBOL_GPL(dma_buf_move_notify); * vmalloc space might be limited and result in vmap calls failing. * * Interfaces:: + * * void \*dma_buf_vmap(struct dma_buf \*dmabuf) * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr) * * The vmap call can fail if there is no vmap support in the exporter, or if - * it runs out of vmalloc space. Fallback to kmap should be implemented. Note - * that the dma-buf layer keeps a reference count for all vmap access and - * calls down into the exporter's vmap function only when no vmapping exists, - * and only unmaps it once. Protection against concurrent vmap/vunmap calls is - * provided by taking the dma_buf->lock mutex. + * it runs out of vmalloc space. Note that the dma-buf layer keeps a reference + * count for all vmap access and calls down into the exporter's vmap function + * only when no vmapping exists, and only unmaps it once. Protection against + * concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex. * * - For full compatibility on the importer side with existing userspace * interfaces, which might already support mmap'ing buffers. This is needed in @@ -1098,6 +1098,11 @@ static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf, * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is * it guaranteed to be coherent with other DMA access. * + * This function will also wait for any DMA transactions tracked through + * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit + * synchronization this function will only ensure cache coherency, callers must + * ensure synchronization with such DMA transactions on their own. + * * Can return negative error values, returns 0 on success. */ int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, @@ -1199,7 +1204,10 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap); * This call may fail due to lack of virtual mapping address space. * These calls are optional in drivers. The intended use for them * is for mapping objects linear in kernel space for high use objects. - * Please attempt to use kmap/kunmap before thinking about these interfaces. + * + * To ensure coherency users must call dma_buf_begin_cpu_access() and + * dma_buf_end_cpu_access() around any cpu access performed through this + * mapping. * * Returns 0 on success, or a negative errno code otherwise. */ diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index cf72699cb2bc..7eca37c8b10c 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -183,24 +183,19 @@ struct dma_buf_ops { * @begin_cpu_access: * * This is called from dma_buf_begin_cpu_access() and allows the - * exporter to ensure that the memory is actually available for cpu - * access - the exporter might need to allocate or swap-in and pin the - * backing storage. The exporter also needs to ensure that cpu access is - * coherent for the access direction. The direction can be used by the - * exporter to optimize the cache flushing, i.e. access with a different + * exporter to ensure that the memory is actually coherent for cpu + * access. The exporter also needs to ensure that cpu access is coherent + * for the access direction. The direction can be used by the exporter + * to optimize the cache flushing, i.e. access with a different * direction (read instead of write) might return stale or even bogus * data (e.g. when the exporter needs to copy the data to temporary * storage). * - * This callback is optional. + * Note that this is both called through the DMA_BUF_IOCTL_SYNC IOCTL + * command for userspace mappings established through @mmap, and also + * for kernel mappings established with @vmap. * - * FIXME: This is both called through the DMA_BUF_IOCTL_SYNC command - * from userspace (where storage shouldn't be pinned to avoid handing - * de-factor mlock rights to userspace) and for the kernel-internal - * users of the various kmap interfaces, where the backing storage must - * be pinned to guarantee that the atomic kmap calls can succeed. Since - * there's no in-kernel users of the kmap interfaces yet this isn't a - * real problem. + * This callback is optional. * * Returns: * @@ -216,9 +211,7 @@ struct dma_buf_ops { * * This is called from dma_buf_end_cpu_access() when the importer is * done accessing the CPU. The exporter can use this to flush caches and - * unpin any resources pinned in @begin_cpu_access. - * The result of any dma_buf kmap calls after end_cpu_access is - * undefined. + * undo anything else done in @begin_cpu_access. * * This callback is optional. * From patchwork Fri Dec 11 15:58:41 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11968553 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D371C4361B for ; Fri, 11 Dec 2020 15:59:00 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B4BC3206D5 for ; Fri, 11 Dec 2020 15:58:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B4BC3206D5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 284E66E442; Fri, 11 Dec 2020 15:58:53 +0000 (UTC) Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by gabe.freedesktop.org (Postfix) with ESMTPS id E7A7A6E423 for ; Fri, 11 Dec 2020 15:58:51 +0000 (UTC) Received: by mail-wr1-x442.google.com with SMTP id a11so1800409wrr.13 for ; Fri, 11 Dec 2020 07:58:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=WhXmefZSTvpDKo6owjq5Ccn4MusL6HQNqDzqvbjA8sQ=; b=cNOr3dLxtzI2QvQqYFVEzfqa8VVJ4YiIkHOgGFULgtgCffkobMbFsvN1yFSxmZ9BA8 3TloSl+PNgRPLIa4Y/DYnCWRHNkWxcFpym/HLTeNjIPss3UJJgaSw10FfmmIQHlJgveE kIwZ0qf7O/BGvw4nocPe8a+sUMFSDS0MdlEHw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=WhXmefZSTvpDKo6owjq5Ccn4MusL6HQNqDzqvbjA8sQ=; b=X25R8sJqdmOJfGKXjzL9QQ1xDnJ9uOaibv3Uuenm1X3rNpXzfdbmP5yInPWcMt/jRS yxNk2RUeFHJVu/Ul7cdSdT5Gflyv2Tra/PCNWrjeND3UbAifO7BWIAHk+FN16gacMvWh F5kjo6uFhjB3AJniOHgXO8PFNomV7MYiBQJ1In6RkcxHY0nlcECNOLeWuAaNNvkqvXYO IRhC7m0GWLvIx4eB+4qKKG0G5tgj6r5VJEcrxkZ1pj92bM5uJpsFQUtI3PGlF815vNTd JLloTY/JBsldcFSPXEYlAluz4m06HEz8mkAXThtO7O17CL73E774QWWCXoTXxnr0H06o H8PQ== X-Gm-Message-State: AOAM530irnbzm6SYtXCzSdRoHRUB39kr8VHNc/WBLSVaPFB7UxuHEVqJ J2HAOmrxW5Ls/GnyFLEvoIEV/Q== X-Google-Smtp-Source: ABdhPJx7XkrQjyR6z/zdr9E40WSHhaMnGSXMi/aJH+IRKynp9hSMVKO5IZBtxkA1arAvCDv7CHd8XQ== X-Received: by 2002:adf:a441:: with SMTP id e1mr14535904wra.385.1607702330609; Fri, 11 Dec 2020 07:58:50 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id z21sm14828241wmk.20.2020.12.11.07.58.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Dec 2020 07:58:49 -0800 (PST) From: Daniel Vetter To: DRI Development Date: Fri, 11 Dec 2020 16:58:41 +0100 Message-Id: <20201211155843.3348718-2-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201211155843.3348718-1-daniel.vetter@ffwll.ch> References: <20201211155843.3348718-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH 2/4] dma-buf: some kerneldoc formatting fixes X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter , Intel Graphics Development , Sumit Semwal , linaro-mm-sig@lists.linaro.org, Thomas Zimmermann , Daniel Vetter , =?utf-8?q?Christian_K=C3=B6nig?= , linux-media@vger.kernel.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Noticed while reviewing the output. Adds a bunch more links and fixes the function interface quoting. Signed-off-by: Daniel Vetter Cc: Thomas Zimmermann Cc: Sumit Semwal Cc: "Christian König" Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org --- drivers/dma-buf/dma-buf.c | 31 ++++++++++++++++++------------- include/linux/dma-buf.h | 6 +++--- 2 files changed, 21 insertions(+), 16 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index a12fdffa130f..e1fa6c6f02c4 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -480,7 +480,7 @@ static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags) * * 4. Once a driver is done with a shared buffer it needs to call * dma_buf_detach() (after cleaning up any mappings) and then release the - * reference acquired with dma_buf_get by calling dma_buf_put(). + * reference acquired with dma_buf_get() by calling dma_buf_put(). * * For the detailed semantics exporters are expected to implement see * &dma_buf_ops. @@ -496,9 +496,10 @@ static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags) * by the exporter. see &struct dma_buf_export_info * for further details. * - * Returns, on success, a newly created dma_buf object, which wraps the - * supplied private data and operations for dma_buf_ops. On either missing - * ops, or error in allocating struct dma_buf, will return negative error. + * Returns, on success, a newly created struct dma_buf object, which wraps the + * supplied private data and operations for struct dma_buf_ops. On either + * missing ops, or error in allocating struct dma_buf, will return negative + * error. * * For most cases the easiest way to create @exp_info is through the * %DEFINE_DMA_BUF_EXPORT_INFO macro. @@ -584,7 +585,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info) EXPORT_SYMBOL_GPL(dma_buf_export); /** - * dma_buf_fd - returns a file descriptor for the given dma_buf + * dma_buf_fd - returns a file descriptor for the given struct dma_buf * @dmabuf: [in] pointer to dma_buf for which fd is required. * @flags: [in] flags to give to fd * @@ -608,10 +609,10 @@ int dma_buf_fd(struct dma_buf *dmabuf, int flags) EXPORT_SYMBOL_GPL(dma_buf_fd); /** - * dma_buf_get - returns the dma_buf structure related to an fd - * @fd: [in] fd associated with the dma_buf to be returned + * dma_buf_get - returns the struct dma_buf related to an fd + * @fd: [in] fd associated with the struct dma_buf to be returned * - * On success, returns the dma_buf structure associated with an fd; uses + * On success, returns the struct dma_buf associated with an fd; uses * file's refcounting done by fget to increase refcount. returns ERR_PTR * otherwise. */ @@ -653,8 +654,7 @@ void dma_buf_put(struct dma_buf *dmabuf) EXPORT_SYMBOL_GPL(dma_buf_put); /** - * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list; optionally, - * calls attach() of dma_buf_ops to allow device-specific attach functionality + * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list * @dmabuf: [in] buffer to attach device to. * @dev: [in] device to be attached. * @importer_ops: [in] importer operations for the attachment @@ -663,6 +663,9 @@ EXPORT_SYMBOL_GPL(dma_buf_put); * Returns struct dma_buf_attachment pointer for this attachment. Attachments * must be cleaned up by calling dma_buf_detach(). * + * Optionally this calls &dma_buf_ops.attach to allow device-specific attach + * functionality. + * * Returns: * * A pointer to newly created &dma_buf_attachment on success, or a negative @@ -769,12 +772,13 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, EXPORT_SYMBOL_GPL(dma_buf_attach); /** - * dma_buf_detach - Remove the given attachment from dmabuf's attachments list; - * optionally calls detach() of dma_buf_ops for device-specific detach + * dma_buf_detach - Remove the given attachment from dmabuf's attachments list * @dmabuf: [in] buffer to detach from. * @attach: [in] attachment to be detached; is free'd after this call. * * Clean up a device attachment obtained by calling dma_buf_attach(). + * + * Optionally this calls &dma_buf_ops.detach for device-specific detach. */ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) { @@ -1061,11 +1065,12 @@ EXPORT_SYMBOL_GPL(dma_buf_move_notify); * shootdowns would increase the complexity quite a bit. * * Interface:: + * * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*, * unsigned long); * * If the importing subsystem simply provides a special-purpose mmap call to - * set up a mapping in userspace, calling do_mmap with dma_buf->file will + * set up a mapping in userspace, calling do_mmap with &dma_buf.file will * equally achieve that for a dma-buf object. */ diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 7eca37c8b10c..43802a31b25d 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -85,10 +85,10 @@ struct dma_buf_ops { /** * @pin: * - * This is called by dma_buf_pin and lets the exporter know that the + * This is called by dma_buf_pin() and lets the exporter know that the * DMA-buf can't be moved any more. * - * This is called with the dmabuf->resv object locked and is mutual + * This is called with the &dmabuf.resv object locked and is mutual * exclusive with @cache_sgt_mapping. * * This callback is optional and should only be used in limited use @@ -103,7 +103,7 @@ struct dma_buf_ops { /** * @unpin: * - * This is called by dma_buf_unpin and lets the exporter know that the + * This is called by dma_buf_unpin() and lets the exporter know that the * DMA-buf can be moved again. * * This is called with the dmabuf->resv object locked and is mutual From patchwork Fri Dec 11 15:58:42 2020 Content-Type: text/plain; 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Fri, 11 Dec 2020 07:58:51 -0800 (PST) From: Daniel Vetter To: DRI Development Date: Fri, 11 Dec 2020 16:58:42 +0100 Message-Id: <20201211155843.3348718-3-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201211155843.3348718-1-daniel.vetter@ffwll.ch> References: <20201211155843.3348718-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH 3/4] dma-buf: begin/end_cpu might lock the dma_resv lock X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter , Intel Graphics Development , Sumit Semwal , linaro-mm-sig@lists.linaro.org, Thomas Zimmermann , Daniel Vetter , =?utf-8?q?Christian_K=C3=B6nig?= , linux-media@vger.kernel.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" At least amdgpu and i915 do, so lets just document this as the rule. Signed-off-by: Daniel Vetter Cc: Thomas Zimmermann Cc: Sumit Semwal Cc: "Christian König" Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Reported-by: kernel test robot Reviewed-by: Christian König --- drivers/dma-buf/dma-buf.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index e1fa6c6f02c4..00d5afe904cc 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -1118,6 +1118,8 @@ int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, if (WARN_ON(!dmabuf)) return -EINVAL; + might_lock(&dma_buf->resv.lock); + if (dmabuf->ops->begin_cpu_access) ret = dmabuf->ops->begin_cpu_access(dmabuf, direction); @@ -1151,6 +1153,8 @@ int dma_buf_end_cpu_access(struct dma_buf *dmabuf, WARN_ON(!dmabuf); + might_lock(&dma_buf->resv.lock); + if (dmabuf->ops->end_cpu_access) ret = dmabuf->ops->end_cpu_access(dmabuf, direction); From patchwork Fri Dec 11 15:58:43 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11968557 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55F7AC1B0D8 for ; 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Fri, 11 Dec 2020 07:58:53 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id z21sm14828241wmk.20.2020.12.11.07.58.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Dec 2020 07:58:52 -0800 (PST) From: Daniel Vetter To: DRI Development Date: Fri, 11 Dec 2020 16:58:43 +0100 Message-Id: <20201211155843.3348718-4-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201211155843.3348718-1-daniel.vetter@ffwll.ch> References: <20201211155843.3348718-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH 4/4] dma-buf: doc polish for pin/unpin X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter , Intel Graphics Development , Sumit Semwal , linaro-mm-sig@lists.linaro.org, Thomas Zimmermann , Daniel Vetter , =?utf-8?q?Christian_K=C3=B6nig?= , linux-media@vger.kernel.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Motivated by a discussion with Christian and Thomas: Try to untangle a bit what's relevant for importers and what's relevant for exporters. Also add an assert that really only dynamic importers use the api function, anything else doesn't make sense. Signed-off-by: Daniel Vetter Cc: Thomas Zimmermann Cc: Sumit Semwal Cc: "Christian König" Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org --- drivers/dma-buf/dma-buf.c | 19 ++++++++++++++++--- include/linux/dma-buf.h | 8 +++++--- 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 00d5afe904cc..1065545e9ca1 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -809,9 +809,15 @@ EXPORT_SYMBOL_GPL(dma_buf_detach); /** * dma_buf_pin - Lock down the DMA-buf - * * @attach: [in] attachment which should be pinned * + * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may + * call this, and only for limited use cases like scanout and not for temporary + * pin operations. It is not permitted to allow userspace to pin arbitrary + * amounts of buffers through this interface. + * + * Buffers must be unpinned by calling dma_buf_unpin(). + * * Returns: * 0 on success, negative error code on failure. */ @@ -820,6 +826,8 @@ int dma_buf_pin(struct dma_buf_attachment *attach) struct dma_buf *dmabuf = attach->dmabuf; int ret = 0; + WARN_ON(!dma_buf_attachment_is_dynamic(attach)); + dma_resv_assert_held(dmabuf->resv); if (dmabuf->ops->pin) @@ -830,14 +838,19 @@ int dma_buf_pin(struct dma_buf_attachment *attach) EXPORT_SYMBOL_GPL(dma_buf_pin); /** - * dma_buf_unpin - Remove lock from DMA-buf - * + * dma_buf_unpin - Unpin a DMA-buf * @attach: [in] attachment which should be unpinned + * + * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move + * any mapping of @attach again and inform the importer through + * &dma_buf_attach_ops.move_notify. */ void dma_buf_unpin(struct dma_buf_attachment *attach) { struct dma_buf *dmabuf = attach->dmabuf; + WARN_ON(!dma_buf_attachment_is_dynamic(attach)); + dma_resv_assert_held(dmabuf->resv); if (dmabuf->ops->unpin) diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 43802a31b25d..628681bf6c99 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -86,13 +86,15 @@ struct dma_buf_ops { * @pin: * * This is called by dma_buf_pin() and lets the exporter know that the - * DMA-buf can't be moved any more. + * DMA-buf can't be moved any more. The exporter should pin the buffer + * into system memory to make sure it is generally accessible by other + * devices. * * This is called with the &dmabuf.resv object locked and is mutual * exclusive with @cache_sgt_mapping. * - * This callback is optional and should only be used in limited use - * cases like scanout and not for temporary pin operations. + * This is called automatically for non-dynamic importers from + * dma_buf_attach(). * * Returns: *